The old-school conventional wisdom about general elections is that you’ve got your partisans who love your candidate and don’t love the other one, and then your independents who are up for grabs but who really can’t stand negative campaigning. If we’ve learned anything about independents in recent years, it’s that the treatment of them as centrist “swing voters” is a gross oversimplification and perhaps just plain wrong. For one thing, most of them (these days at least) are functional partisans whose “lean” toward one party or another is a pretty reliable predictor of how they will ultimatelyvote.

But a new analysis of indies from Pew offers fresh and fascinating insight about what makes these “indie leaners” tick. They differ from regular partisans by not particularly sharing the warm feelings toward the party to which they “lean.” But what they do share abundantly is the partisan’s antipathy toward the party to which they do not“lean.”

A majority of Republican leaners (55%) and roughly half of Democratic leaners (51%) cite the other party’s policies being bad for the country as a major reason why they lean toward their own party. By contrast, just 30% of Republican leaners and 34% of Democratic leaners say that their own party’s policies being good for the country is a major reason why they lean toward theirparty.

The intensity of this negative feeling toward the other party among “leaners” has grown rapidly along with partisan polarizationgenerally:

Today, 44% of Republican and Democratic leaners say they have a very unfavorable impression of the opposing party, up from just 10% and 11% respectively in1994.

There are two pretty obvious implications of this finding: First, attacking the other party is the best way to remind your least loyal voters why they favor you; and second, “negative” campaigning may be the best strategy for maintaining and strengthening party unity. There’s one more finding relevant to this secondpoint:

So the idea that negative campaigning pits partisans against indies would not seem to be accurate at all, at least when it comes to the big majority of indies who “lean.” In the current presidential contest, each major-party candidate has a problem with lukewarm support from big elements of her or his own party — but represents an exaggerated version of everything the other party’s supporters fear about them. In such circumstances it’s almost political malfeasance not to go negative and stay negative to the very bitterend.